首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1011篇
  免费   46篇
  国内免费   146篇
安全科学   17篇
环保管理   177篇
综合类   520篇
基础理论   300篇
污染及防治   22篇
评价与监测   47篇
社会与环境   110篇
灾害及防治   10篇
  2024年   6篇
  2023年   6篇
  2022年   18篇
  2021年   22篇
  2020年   24篇
  2019年   25篇
  2018年   25篇
  2017年   40篇
  2016年   42篇
  2015年   48篇
  2014年   34篇
  2013年   59篇
  2012年   72篇
  2011年   84篇
  2010年   64篇
  2009年   68篇
  2008年   59篇
  2007年   66篇
  2006年   68篇
  2005年   75篇
  2004年   42篇
  2003年   57篇
  2002年   32篇
  2001年   39篇
  2000年   30篇
  1999年   33篇
  1998年   10篇
  1997年   6篇
  1996年   17篇
  1995年   7篇
  1994年   9篇
  1993年   2篇
  1992年   2篇
  1990年   2篇
  1989年   1篇
  1987年   1篇
  1986年   1篇
  1984年   4篇
  1981年   1篇
  1980年   2篇
排序方式: 共有1203条查询结果,搜索用时 46 毫秒
51.
52.
Fire influences the distribution of fauna in terrestrial biomes throughout the world. Use of fire to achieve a mosaic of vegetation in different stages of succession after burning (i.e., patch‐mosaic burning) is a dominant conservation practice in many regions. Despite this, knowledge of how the spatial attributes of vegetation mosaics created by fire affect fauna is extremely scarce, and it is unclear what kind of mosaic land managers should aim to achieve. We selected 28 landscapes (each 12.6 km2) that varied in the spatial extent and diversity of vegetation succession after fire in a 104,000 km2 area in the semiarid region of southeastern Australia. We surveyed for reptiles at 280 sites nested within the 28 landscapes. The landscape‐level occurrence of 9 of the 22 species modeled was associated with the spatial extent of vegetation age classes created by fire. Biogeographic context and the extent of a vegetation type influenced 7 and 4 species, respectively. No species were associated with the diversity of vegetation ages within a landscape. Negative relations between reptile occurrence and both extent of recently burned vegetation (≤10 years postfire, n = 6) and long unburned vegetation (>35 years postfire, n = 4) suggested that a coarse‐grained mosaic of areas (e.g. >1000 ha) of midsuccessional vegetation (11–35 years postfire) may support the fire‐sensitive reptile species we modeled. This age class coincides with a peak in spinifex cover, a keystone structure for reptiles in semiarid and arid Australia. Maintaining over the long term a coarse‐grained mosaic of large areas of midsuccessional vegetation in mallee ecosystems will need to be balanced against the short‐term negative effects of large fires on many reptile species and a documented preference by species from other taxonomic groups, particularly birds, for older vegetation. Mosaicos de Fuego y la Conservación de Reptiles en una Región Propensa al Fuego  相似文献   
53.
Abstract: We reviewed the evidence on the extent and efficacy of conservation of tropical forest biodiversity for each of the classes of conservation action defined by the new International Union for Conservation of Nature (IUCN) classification. Protected areas are the most tested conservation approach, and a number of studies show they are generally effective in slowing deforestation. There is some documentation of the extent of sustainable timber management in tropical forest, but little information on other landscape‐conservation tactics. The extent and effectiveness of ex situ species conservation is quite well known. Forty‐one tropical‐forest species now survive only in captivity. Other single‐species conservation actions are not as well documented. The potential of policy mechanisms, such as international conventions and provision of funds, to slow extinctions in tropical forests is considerable, but the effects of policy are difficult to measure. Finally, interventions to promote tropical conservation by supporting education and livelihoods, providing incentives, and furthering capacity building are all thought to be important, but their extent and effectiveness remain poorly known. For birds, the best studied taxon, the sum of such conservation actions has averted one‐fifth of the extinctions that would otherwise have occurred over the last century. Clearly, tropical forest conservation works, but more is needed, as is critical assessment of what works in what circumstances, if mass extinction is to be averted.  相似文献   
54.
Abstract: We examined how differences in local forest‐management institutions relate to disparate anthropogenic forest disturbance and forest conditions among three neighboring montane forests in Tanzania under centralized, comanaged, or communal management. Institutional differences have been shaped by decentralization reforms. We conducted semistructured interviews with members of forest management committees, local government, and village households and measured anthropogenic disturbance, tree structure, and species composition in forest plots. We assessed differences in governance system components of local institutions, including land tenure, decision‐making autonomy by forest users, and official and de facto processes of rule formation, monitoring, and enforcement among the three management strategies. We also assessed differences in frequencies of prohibited logging and subsistence pole cutting, and measures of forest condition. An adjacent research forest served as an ecological reference for comparison of forest conditions. Governance was similar for comanaged and centralized management, whereas communal managers had greater tenure security and decision‐making autonomy over the use and management of their forest. There was significantly less illegal logging in the communal forest, but subsistence pole cutting was common across all management strategies. The comanaged forest was most disturbed by recent logging and pole cutting, as were peripheral areas of the larger centralized forest. This manifested in more degraded indicators of forest conditions (lower mean tree size, basal area, density of trees ≥ 90 cm dbh, and aboveground biomass and higher overall stem density). Greater tenure security and institutional autonomy of the communal strategy contributed to more effective management, less illegal logging, and maintenance of good forest conditions, but generating livelihood benefits was a challenge for both decentralized strategies. Our results underscore the importance of well‐designed institutional arrangements in forest management and illustrate mechanisms for improved forest governance and conservation in the context of Tanzanian decentralization reforms.  相似文献   
55.
An evaluation of coastal landscape of pine forest in Greece by summer visitors of various nationalities was carried out. The visual preferences for a set of landscape, represented in photographs, expressed by these various nationality groups were compared. The subjects used in this research came from Greece, Germany, Italy, France, Great Britain, Austria, Yugoslavia, and Scandinavian countries. The findings show that there is an agreement over the basic preference, but, nevertheless, there are differences of opinion between the nationality groups that might be attributed to cultural influences and the effect of being familiar with their own environments. Since coastal landscape plays an important role in the tourist industry, these findings could be very useful to policy-making agencies.  相似文献   
56.
The study attempts to separate the effects of forest fragmentation related to landscape (patch area, isolation) and habitat (altitude, vegetation structure) on bird community composition in a mountain pine forest. Bird composition was related, using a multivariate approach (canonical correspondence analyses), to either habitat or to landscape, eliminating the effect of habitat statistically. Bird composition and species richness varied with patch area and isolation from large pine stands, but this effect could be assigned principally to variation in vegetation structure and altitude. Another effect, that of increasing occurrence and numbers of Anthus trivialis with decreasing distance to nearest low-altitude forest, could be assigned to both habitat (grass cover) and landscape (connectivity effects). Management implications are drawn from the results.  相似文献   
57.
景观生态学在建设项目生态环境影响评价中的应用   总被引:13,自引:0,他引:13  
田红  何晓静 《四川环境》2003,22(4):13-15,22
景观生态学目前是国家环境保护总局《非污染生态影响评价技术导则》引入的概念框架和理论方法。本文通过景观生态学在不同性质建设项目中的运用分析,进行了一定的尝试,更加希望在今后建设项目生态环境影响评价工作中得到修正和完善。  相似文献   
58.
市容环境是与公众生活联系最为紧密的领域,也是公众参与最容易进行的领域。南京的城市建设要实现“经济发达、环境优美、融古都特色和现代文明于一体的现代化江滨城市”的目标,公众参与市容环境的规划与管理是关键内容之一。论文以“南京市市容环境卫生发展规划”项目工作为基础,分析和阐述公众参与的内涵,提出公众参与市容环境的五大步骤,并针对南京市容环境方面的具体案例,设计出符合南京特色的公众参与市容环境规划与管理的方法框架模型,包括决策模式、制度框架的共管体系。  相似文献   
59.
阜康市生态旅游规划研究   总被引:3,自引:0,他引:3  
生态旅游规划是生态示范区规划的重要组成部分。本文以天池风景区规划为例阐述生态旅游规划应突破以风景区为主单一的旅游景观格局,应根据景观生态学原理、旅游地理学和旅游经济学理论,按照景观格局的梯度性变化为依据,以增长旅游线路、丰富景区类型、提高旅游收入为内容,以保护景区资源、开发景区资源为目标,开展基于发展“大旅游”思想的以沈域为单元的全面战略性规划,为实现阜康产业结构调整、增强区域经济实力提供依据。  相似文献   
60.
丽江古城水环境现状与调控对策研究   总被引:5,自引:0,他引:5  
范弢  杨世瑜 《资源开发与市场》2007,23(2):153-155,192
水环境是丽江世界文化遗产地生态地质环境的重要组成部分。由于丽江城市化进程加快,对水环境保护不力,导致古城水污染加剧、水资源量衰减、景观生态用水不足和景观水质下降。通过强化水环境研究,加强水环境立法,进行水生态环境综合治理;实施以调剂古城周边地下泉水为主,拉市海调水为辅的丽江古城景观调水方案,可保护丽江古城水环境,为丽江古城世界文化遗产地的可持续发展提供保证。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号